TRENTON — Gov. Chris Christie’s new state budget will likely feature a down payment on his signature income tax cut — but he also needs to pay for other promises, including more money for transportation, public employee pensions and last year’s business tax cut.

And he must come up with another $300 million — about twice what his income tax may cost in the budget — to pay down debt that’s left over from the last time New Jersey cut income taxes.

New Jersey taxpayers are still paying off the debt — and at an ever-rising rate — for the pension bonds issued in 1997 by then-Gov. Christie Whitman, who was the last governor to offer a major income tax cut.

Christie’s spending plan is expected to include the first phase of the three-year income tax cut he proposed last month during his State of the State address. The governor, a Republican, will offer his third state budget during an address to lawmakers scheduled for Feb. 21.

If Christie spreads that first installment of the income tax cut out equally over three calendar years, the new budget will need about $150 million to offset the lost revenue, non-partisan legislative budget analysts reported earlier this month.

That’s not a huge amount to find for a state that is spending roughly $30 billion annually.

“Like everything else, I’m going to act in a responsible manner,” the governor said during a recent State House news conference. “That’s why I’m phasing in the income tax cut over three years, not doing it all in one fell swoop.”

But that loss of income tax revenue would hit a budget that also has to absorb Christie’s prior commitment to increase the annual payment into the state pension system.

And he’s also already promised to use more of the budget to fund transportation projects instead of hiking the gas tax.

Senate Budget Committee Chairman Paul Sarlo, D-Wood-Ridge, said the cost of those decisions by the governor is starting to add up for a budget already weighed down by other major items.

“That’s what’s concerning me here,” Sarlo said during a recent committee meeting. “We have an obligation to look to the future.”

The list of budget challenges also includes this year’s $300 million payment toward the debt incurred by former Republican Gov. Christie Whitman. In 1997, the state borrowed $2.8 billion to plug a hole in its pension funds. Money that would have gone into the pension funds was freed to be used for the state budget, covering any revenue lost by Whitman’s tax cut.

Here’s a closer look at some of the biggest challenges Christie has to confront as he finalizes the new budget.

New Jersey is carrying a pension fund deficit of nearly $42 billion after years of mismanagement and skipped payments by politicians in Trenton. The governor worked with Democrats last year and in 2010 to enact widespread public employee benefit reforms, and the unfunded liability in the pension system would be worse if those changes weren’t made.

But the reforms included a new law that requires the state to start working toward full payment of its annual obligation into the investment fund that helps pay pension benefits. That meant, after years of skipped payments, a $484 million payment from the current budget into the pension fund. This year, the payment could rise to near $1 billion depending on what actuaries say is required.

Overspending and heavy borrowing by prior governors left the state’s funding system for transportation projects in disarray by the time Christie arrived in Trenton in 2010. The gas tax pays for the projects, but most of this year’s revenue has been leveraged by previous governors, leaving little cash for new improvements.

The governor has refused to raise the gas tax to keep up transportation spending. Instead, he’s implementing a plan that relies on some new borrowing and some funding from outside agencies such as the Port Authority of New York and New Jersey, as well as $261 million carved out of the state budget.

Long after state residents received the break provided by Whitman’s income tax cut, they are still paying off the debt critics say made it possible. Debt service on the 1997 bond sale floated by Whitman will rise to close to $300 million in the new budget, twice the assumed first-year cost of Christie’s proposed income tax cut. The annual payments for Whitman’s bond issue become an even bigger headache over the next decade, increasing to $500 million by 2022.

The governor enacted a series of business tax cuts last year that received much less attention than the income tax cut he’s proposed in 2012. But those cuts cost an estimated $185 million during the current budget year, more than the assumed first-year price tag of his proposed income tax cut. The governor promoted the business tax cuts as a way to grow the state economy and create jobs. He is not expected to roll them back after only one year, meaning the lost revenue from the cuts would continue in the new budget unless economic recovery speeds up and they begin paying for themselves.

Christie projected state revenue would grow by 5 percent during the current budget year, but unemployment is at 9 percent — higher than other states in the region — and tax collections have not lived up to forecasts in the first six months. The gap between tax collections and the projections included in the budget was $325 million, or about 3 percent, through the end of December. If that shortfall holds through the end of the budget year, Christie will have to make spending cuts or raid surplus because the state constitution doesn’t allow a deficit. But if the revenue picture improves by Feb. 21, and his economic advisers see more recovery looming, the increased revenue will help ease many budget problems.